Objective: Current methods used to measure incidence of traumatic brain injury (TBI) underestimate its true public health burden. The use of self-report surveys may be an approach to improve these estimates. An important step in public health surveillance is to define a public health problem using a case definition. The purpose of this article is to outline the process that the Centers for Disease Control and Prevention undertook to refine a TBI case definition to be used in surveillance using a self-report survey.
Setting: Survey.
Participants: A total of 10 030 adults participated via a random digit-dial telephone survey from September 2018 to September 2019.
Main measures: Respondents were asked whether they had sustained a hit to the head in the preceding 12 months and whether they experienced a series of 12 signs and symptoms as a result of this injury.
Design: Head injuries with 1 or more signs/symptoms reported were initially categorized into a 3-tiered TBI case definition (probable TBI, possible TBI, and delayed possible TBI), corresponding to the level of certainty that a TBI occurred. Placement in a tier was compared with a range of severity measures (whether medical evaluation was sought, time to symptom resolution, self-rated social and work functioning); case definition tiers were then modified in a stepwise fashion to maximize differences in severity between tiers.
Results: There were statistically significant differences in the severity measure between cases in the probable and possible TBI tiers but not between other tiers. Timing of symptom onset did not meaningfully differentiate between cases on severity measures; therefore, the delayed possible tier was eliminated, resulting in 2 tiers: probable and possible TBI.
Conclusion: The 2-tiered TBI case definition that was derived from this analysis can be used in future surveillance efforts to differentiate cases by certainty and from noncases for the purpose of reporting TBI prevalence and incidence estimates. The refined case definition can help researchers increase the confidence they have in reporting survey respondents' self-reported TBIs as well as provide them with the flexibility to report an expansive (probable + possible TBI) or more conservative (probable TBI only) estimate of TBI prevalence.